In a medium mixing bowl, whisk together the pumpkin puree, eggs, granulated sugar, brown sugar, pumpkin pie spice, and 1 teaspoon of the cinnamon until well combined.
Add the evaporated milk and stir well. Pour the mixture into a large crockpot (4-6 quarts) that has been lightly coated with non-stick cooking spray.
In a medium mixing bowl, whisk together the cake mix with the remaining 1 teaspoon of cinnamon. Stir in the melted butter (the mixture will be crumbly). Sprinkle this cake mixture all over the top of the pumpkin mix inside the Crockpot.
Cover and set to low and cook for 4 hours. Sprinkle the nuts over the top about halfway through the cooking time if desired. Serve the cobbler warm with ice cream or whipped cream on top.